Buggy code:
public final class SurveyResponseValidators { private SurveyResponseValidators ( ) { } public static Set < String > validateSurveyIds ( final String surveyIds ) throws ValidationException { } public static Set < String > validatePromptIds ( final String promptIds ) throws ValidationException { } public static UUID validateSurveyResponseId ( final String surveyId ) throws ValidationException { } public static Set < UUID > validateSurveyResponseIds ( final String surveyResponseIds ) throws ValidationException { } public static PrivacyState validatePrivacyState ( final String privacyState ) throws ValidationException { } public static Set < String > validateUsernames ( final String usernames ) throws ValidationException { } public static Set < SurveyResponse . ColumnKey > validateColumnList ( final String columnList ) throws ValidationException { } public static OutputFormat validateOutputFormat ( final String outputFormat ) throws ValidationException { } public static List < SortParameter > validateSortOrder ( final String sortOrder ) throws ValidationException { if ( StringUtils . isEmptyOrWhitespaceOnly ( sortOrder ) ) { <START_BUG> return SurveyResponseReadRequest . DEFAULT_SORT_ORDER ; <END_BUG> } List < SortParameter > result = new ArrayList < SortParameter > ( 3 ) ; String [ ] sortOrderArray = sortOrder . split ( LIST_ITEM_SEPARATOR ) ; for ( int i = 0 ; i < ( sortOrderArray . length ) ; i ++ ) { SortParameter currSortParameter ; try { currSortParameter = SortParameter . getValue ( sortOrderArray [ i ] . trim ( ) ) ; } catch ( IllegalArgumentException e ) { throw new ValidationException ( ErrorCode . SURVEY_INVALID_SORT_ORDER , ( "An<seq2seq4repair_space>unknown<seq2seq4repair_space>sort<seq2seq4repair_space>order<seq2seq4repair_space>value<seq2seq4repair_space>was<seq2seq4repair_space>given:<seq2seq4repair_space>" + ( sortOrderArray [ i ] ) ) ) ; } if ( result . contains ( currSortParameter ) ) { throw new ValidationException ( ErrorCode . SURVEY_INVALID_SORT_ORDER , ( "The<seq2seq4repair_space>same<seq2seq4repair_space>sort<seq2seq4repair_space>order<seq2seq4repair_space>value<seq2seq4repair_space>was<seq2seq4repair_space>given<seq2seq4repair_space>multiple<seq2seq4repair_space>times:<seq2seq4repair_space>" + ( currSortParameter . toString ( ) ) ) ) ; } else { result . add ( currSortParameter ) ; } } if ( ( result . size ( ) ) != ( SortParameter . values ( ) . length ) ) { throw new ValidationException ( ErrorCode . SURVEY_INVALID_SORT_ORDER , ( ( ( ( "There<seq2seq4repair_space>are<seq2seq4repair_space>" + ( SortParameter . values ( ) . length ) ) + "<seq2seq4repair_space>sort<seq2seq4repair_space>order<seq2seq4repair_space>values<seq2seq4repair_space>and<seq2seq4repair_space>" ) + ( result . size ( ) ) ) + "<seq2seq4repair_space>were<seq2seq4repair_space>given." ) ) ; } return result ; } public static Function validateFunction ( final String function ) throws ValidationException { } public static Set < FunctionPrivacyStateItem > validatePrivacyStateGroupList ( final String list ) throws ValidationException { } public static Date validateStartDate ( final String startDate ) throws ValidationException { } public static Date validateEndDate ( final String endDate ) throws ValidationException { } public static Boolean validateSuppressMetadata ( final String suppressMetadata ) throws ValidationException { } public static Boolean validateReturnId ( final String returnId ) throws ValidationException { } public static Boolean validatePrettyPrint ( final String prettyPrint ) throws ValidationException { } public static Boolean validateCollapse ( final String collapse ) throws ValidationException { } public static long validateNumSurveyResponsesToSkip ( final String surveyResponsesToSkip ) throws ValidationException { } public static long validateNumSurveyResponsesToProcess ( final String surveyResponsesToProcess , final long limit ) throws ValidationException { } private static Boolean validateOptionalBoolean ( final String booleanString , final ErrorCode errorCode , final String errorMessage ) throws ValidationException { } }

Fix:
return null ;